Copernicus is the only freeware desktop recorder for Mac OS that I know, but it can only capture pictures and video (there is no support for recording audio).

Freeware Capture Me can also record video without sound, but it allows to record one minute long movies only!

You can also use online screen recorders:

• Screen Toaster (Mac OS X, Windows, Linux)
• Screencast-O-Matic (Mac OS, Windows)
• Jing

Note that free basic versions limit the formats that you can use and recording time.